Patent GB-1099835-A (GB)
Title: Electronic clock
IPC: G04G3/02
Filed: 1965-07-07
Abstract: 1,099,835. Pulse frequency dividing. INTERNATIONAL BUSINESS MACHINES CORPORATION. July 7, 1965 [July 8, 1964], No. 28774/65. Heading H3P. [Also in Division G4] A clock pulse generator of widely variable interval comprises means for producing a pulse sequence on a delay line, means responsive to a sequence of pulses at a second point on the line to initiate another pulse sequence on the line, and means responsive to a predetermined pulse sequence on the line to give an output. In the Figure the circuit receives pulses at 10 and gives out pulses at longer intervals at 11. Oscillator 29 controls the phase of the pulses, and driver 26 launches a pulse on the delay line 12 whenever activated by AND gate 30, which in turn is controlled by the input pulses 10. The presence of pulses at Y and Z on the line is sensed and applied to shift cells 16 which delay the pulses slightly for trimming the effective length of the line and locking the pulses in phase with the oscillator output. When pulses enter at 10, a single-shot circuit 40 energizes OR gate 34, AND gate 30 and driver 26 to produce a " tag " pulse on the line 12. This tag pulse is sensed at Y and recirculated through shift cell 16, AND gate 41 and OR gate 32. At the same time the pulse at Y is inverted at 45 and applied to AND gate 46. A bi-stable circuit 47 energizes AND gates 41, 46 in turn to apply via OR gate 32 either Y pulses or their complements to the line, the input 50 being continuously energized during this operation of adding one count to the line each time the tag pulse reaches Y. The pulses that follow the tag pulse along the line thus comprise zeros and ones in a sequence determined by the operation of the bi-stable circuit 47. The tag pulse also controls a bi-stable circuit 54, setting it when the tag appears at 17 and resetting it when the tag appears at 18. The bi-stable circuit 54 controls 47 so that whether the latter produces zeros or ones on the line 12 depends on what has arrived at points Y and Z, and this can be adjusted by altering the effective lengths of XY and YZ. The bi-stable circuit 47 is reset by AND gate 46 through OR gate 57 which is alternatively operated by the output pulses at 66. Delay devices 55, 56 have delay times of ¢-¥bit time to allow the AND gate 46 to transmit a sufficiently long pulse before it is closed. Output pulses will be obtained at 11 only at instants when three conditions are satisfied, defined by the three inputs of AND gate 60: (a) a zero at Y applied via inverter 45; (b) tag pulse at Z applied via 18 and 61; (c) bi-stable circuit 47 in " set " condition. Thus the circuit responds to a predetermined sequence of pulses in the line, responding when the tag pulse reaches Z and the first zero appears at Y, there being at this stage a one in each place between Y and Z. In response to this succession of ones a series of zeros appears at input 28 of driver 26, and inverter 65 applies a zero to AND gate 46 to inhibit further transmission of ones to the line. Thus after an output has been produced at 11 the line is cleared ready for the next cycle, the output of AND gate 60 resetting the bistable circuit 47 through OR gate 57. The portion XY of the line is at least twice the effective length of YZ to prevent the line from containing simultaneously a one at Z from one sequence of pulses and a first zero at Y from a next sequence.